Alpha-Amylases (alpha-1,4-glucan-4-glucanohydrolases, EC. 3.2.1.1) constitute a group of enzymes which catalyze hydrolysis of starch and other linear and branched 1,4-glucosidic oligo- and polysaccharides.
There is a very extensive body of patent and scientific literature relating to this industrially very important class of enzymes. A number of alpha-amylase referred to as “Termamyl®-like alpha-amylases” and variants thereof are known from, e.g., WO 90/11352, WO 95/10603, WO 95/26397, WO 96/23873 and WO 96/23874. Termamyl-like alpha-amylases are very thermostable and therefore suitable for processes carried out at high temperatures such as starch liquefaction in dextrose production processes.
Another group of alpha-amylases are referred to as “Fungamyl®-like alpha-amylases”, which are alpha-amylases related to the alpha-amylase derived from Aspergillus oryzae (and shown in SEQ ID NO: 1). These Fungamyl-like alpha-amylases have a relatively low thermostability (the commercial product sold under the tradename FUNGAMYL™ by Novo Nordisk, Denmark, has a optimum around 55° C.) and is therefore not suitable for processes carried out at high temperatures. Fungamyl-like alpha-amylases are today used for making syrups for, e.g., the brewing industry. Such processes are operated at around 60° C. resulting in that usually in the range of double the enzyme dosage must be used to compensate for the low thermostability. Further, at 55° C. infection problems may occur.
As such processes today furthermore are carried out at a pH of 5.5, instead of, e.g., pH 4.5, pH adjustment and addition of Sodium to the syrups are necessitated.
Therefore, it would be advantageous to provide a Fungamyl-like alpha-amylase with increased thermostability preferably at an acidic pH.